The present invention relates to an oil separator. The oil separator includes a case and introduces blow-by gas of an internal combustion engine into the case. The oil separator then separates oil from the blow-by gas and discharges the separated oil from the case.
Internal combustion engines are equipped with a recirculation passage for recirculating blow-by gas in the crank chamber to the intake passage. An oil separator is provided in such a recirculation passage to separate oil mist from the blow-by gas (for example, Japanese Laid-Open Patent Publication No. 3-141811).
The case of the oil separator disclosed in the above publication incorporates two meshed first and second electrodes, which are arranged to face each other. A power supply unit creates a potential difference between the first and second electrodes. In such an oil separator, water contained in blow-by gas is electrically charged when the blow-by gas flows through the first electrode, and the electrically charged water is adsorbed to the second electrode due to electrostatic force. At this time, oil mist contained in the blow-by gas is adsorbed to the second electrode together with the water. The publication states that oil mist contained in the blow-by gas is thus separated from the blow-by gas in this manner. The oil and water adsorbed to the second electrode drop due to the own weight and are discharged from the case through an oil outlet provided in the bottom wall of the case.
In the oil separator disclosed in the above mentioned publication, when the flow velocity of blow-by gas is great, oil is likely to flow through the second electrode without being adsorbed to the second electrode. The oil separator thus has a low oil capture efficiency.
In this respect, the meshes of the second electrode may be made smaller so that oil is easily adsorbed to the second electrode. In this case, however, the small meshes of the second electrode increases the airflow resistance, causing another problem. That is, the pressure loss by the oil separator increases.